package 题目集.数学;

import java.util.Scanner;

public class 互质数不能表示的最大数 {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int a = sc.nextInt();
        int b = sc.nextInt();
        System.out.println(a*b-a-b);
    }
}
